The slave trade had profound consequences on both Africa and the Americas. The full extent of the consequences is huge and too numerous to fully explain here. Below you will find a brief summary of some of the larger consequences of the slave trade in each region.
In Africa, particularly along the coast of West Africa, the slave trade greatly changed the political and social dynamics. Beginning in the 17th Century, more and more European slave traders would go to the African coast to purchase slaves to bring to the New World. They traded with local rulers and merchants who gained power and influence as a result. The trade introduced many foreign goods to Africa, such as firearms and foreign cloths.
The slave trade did lead to near constant warfare between the coastal groups and the peoples of the interior who they targeted as slaves to sell. This led to a stymied economy and a great shortage in the labor force. Even though a large economy developed based on slave catching and trading, few other economic endeavors were pursued as a result. It decimated entire communities and created a gender imbalance as men were more often kidnapped than women.
As time went by, Europeans sought to trade for slaves on their own terms. This resulted in the establishment of slave forts along the coast and the stationing of garrisons in slave-trading ports. As a result, Europeans were better poised to colonize parts of the African continent in the 19th Century when the slave trade had ended.
Of course, the slave trade also had a profound effect in the Americas. It introduced a large population of subjugated individuals. This led to a strong economy with a workforce that was able to find, harvest, process, and transport huge amounts of resources. A wealthy planter and merchant class developed as a result.
The slave trade also had a huge impact on the ethnic makeup of the region. In many places, particularly in the Carribean and Brazil, African slaves mixed with other populations over time to create a unique and blended culture that incorporated indigenous, African, and even some European elements into the society. This was less the case in the United States where slave populations were often kept strictly apart from much of the white population. There, it created a dual society - one made up of the free white population and another made up of slave laborers.
One major consequence that would develop as a result of the slave trade would be divisions among the ruling white classes. As slavery went on, many people began to feel that it was morally wrong to keep people in bondage. Of course, the slave owners who were making huge profits off the backs of their slaves tended to disagree. These disagreements would eventually lead to outbreaks of violence over the issue, most notably the American Civil War.